The present invention relates to spiral coils that can be interlaced to create fabrics or seams for use in the papermaking industry. It further relates to a method for extruding and cutting tubes to produce the coils.
It has been recognized in the prior art that spiral coils can be used to create all or part of a papermaking fabric. The most common spiral coils are made from extruded monofilaments that are thermally treated and wrapped about a mandrel for shaping into a helical form. The resultant coils and fabrics are sensitive to fluctuations in ambient temperature and moisture which leads to their destabilization in use. This tendency to destabilize is believed to be attributable to orientation of the polymer molecules in the monofilament along the longitudinal axis established during the monofilament extrusion process. Conventional prior art methods generally require a coiling process that limits them to certain materials. In addition, the coiled materials generally require further heat setting to achieve a flat or planer coil array. These conditions generally limit the coiling method to round or oval monofilaments which have lower surface contact areas.
The invention is directed to an apparatus or the creation of a spiral coil by extruding a hollow tube and cutting the tube in a fixed plane relative to the tube. Additionally, the invention is directed to a fabric made from such spiral coils.